Increased Soil Water Storage Research Articles

Irrigation and soil surface management in arid soils with surface crust

The effects of irrigation and soil surface management on soil water storage and crop yield were studied in soils affected by surface crust. A field experiment was conducted during 1993/1994 at the University of Jordan Research Station near Al-Muwaqqar village. Soil surface management was the main experimental factor, comprising four treatments: furrows, basins, furrows within basins, and control. Irrigation management was a secondary experimental factor. Water was applied through three different irrigation practices: one, two, and three irrigation sets with the same amount of water per treatment.Soil water storage was improved significantly by 200% and 90% using furrow and basin soil surface treatments, respectively, compared with soil water storage in the control treatment. The advantage of furrows is that water infiltration inside the furrows occurs in two-dimensions: vertical and horizontal. Frequent irrigation (two and three irrigation sets) increased soil water storage by 50%. Furrow soil surface treatments produced significantly better barley emergence and higher barley grain yield than the basin and control treatments. The relative increases in barley grain yield in furrow soil surface treatment compared with basin and control treatments were 32% and 200%, respectively. Thus furrow soil surface treatment and frequent irrigation are recommended for soils suffering from surface crust formation.

Stubble retention and tillage in a semi-arid environment: 1. Soil water accumulation during fallow

A study was carried out over 4 years at two sites in semi-arid, north-west Victoria, Australia, to examine the effect of soil surface management during fallow on water and nitrogen accumulation and their effect on the growth and yield of the subsequent wheat crop. The fallow treatments comprised four combinations of stubble management and tillage in 18-month-long fallows of a fallow-wheat rotation together with a pea-wheat rotation which included an annual short (6 month) tilled summer fallow. The two sites are representative of the major soil types of the region; a chromic vertisol at Dooen and a calcic xerosol at Walpeup. This paper reports observations and analyses of soil water accumulation during the fallow phase. At Dooen, tillage without stubble increased soil water storage, at sowing, on average by 76 mm (range 24–122 mm) above the summer fallow. Stubble retention added a further 52 mm (range 36–65 mm). Zero tillage was beneficial in one year, and was enhanced by the presence of stubble. In contrast, at Walpeup, tillage without stubble provided an average of 37 mm more water at sowing than the summer fallow. Stubble retention without tillage increased water storage by 27 mm in only one year. At both sites the additional water stored due to stubble retention was located deep in the profile to 2.0 m. In general, zero tillage, primarily with stubble retention, offered large and consistent increases in soil water storage on heavy-textured clay soils in a 420-mm rainfall zone. On the lighter, sandy loam soil under the lower rainfall regime (343 mm), the advantage in soil water storage, through both stubble retention and zero tillage, was less frequent.

Cropping Intensity and Nitrogen Management Impact of Dryland No-Till Rotations in the Semi-Arid Western Great Plains

Crop N needs are not usually predicted based on cropping intensity or on tillage practice. However, N fertilizer requirements may increase dramatically as less fallow and less tillage are used in semi-arid regions of the Great Plains where summer fallow cropping is common. This long-term experiment was conducted to study the influence of N fertilizer rate, source/placement/timing (NSP), and crop rotation factors on the production of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor L.), as well as their fertilizer N use efficiency (FNUE) for the initial years of conversion to no-till dryland farming. Research was conducted from 1987 through 1992 on two soils (Keith clay loam, a fine-silty, mixed, mesic Aridic Argiustoll and Weld loam, a fine-silty, mixed, mesic, Aridic Argiustoll) in eastern Colorado. Rotations included winter wheat-fallow (WF) and winter wheat-corn or grain sorghum-fallow (WCF). Wheat yields were similar between WF and WCF with adequate N application. Response to N fertilizer at lower rates was greater in WCF than WF because of its greater depletion of soil N. Corn production averaged 72 bu/acre with adequate N and required 1 Ib/acre of N uptake to produce 1 bu/acre of grain. Current N fertilizer recommendations for wheat and corn were not adequate to insure maximum production under no-till management. Fertilizer placement significantly affected average annual rotational yield (40 to 70 Ib/acre per yr difference) but application rate was more important economically. Grain biomass produced in each rotation per pound of total plant N uptake (GNUE) was 17 Ib/acre per yr in WF compared with 29 Ib/acre per yr for WCF. This 70% increase in average annual grain production of WCF over WF was accomplished with a 44% annual increase in fertilizer N application.

Effect of tillage and stubble management on soil water storage, crop growth and yield in a wheat-lupin rotation in southern NSW

The effects of tillage (conventional tillage v. direct drilling) and stubble management (stubble retained v. stubble burnt) on soil water storage, growth and yield of wheat were assessed over two seasons (1989-1990) in a wheat-lupin rotation on a red earth at Wagga Wagga, NSW. Soil water storage and efficiency of water use were different for the two seasons. Both direct drilling and stubble retention maintained the soil surface (0-0.1 m) at higher water content at sowing time. However, their effectiveness in increasing soil water storage at sowing was evident only in the 1990 season which, with average rainfall during the summer fallow, was drier than 1989. Average wheat grain yield was similar (4.02 v. 4.08 t/ha) for the two seasons even though the 1989 season had 245 mm more rain, the difference mainly occurring in March-April. Most of the excess water in seasons like 1989 was likely to have been lost by deep drainage, with implications for leaching of soluble nutrients, increasing subsoil acidity and rising watertables. Poor early growth of wheat when the stubble was retained and the crops direct drilled was season dependent. It was observed in the wheat crop only in the 1989 season which had a wet autumn. In that season, poor early growth which resulted in a significant yield reduction of 0.5 t/ha was associated with reduced water extraction before anthesis despite the availability of adequate soil water. No corresponding differences in growth and yield were observed for the lupin crop.

Tillage Effects on Thermal Conductivity of Two Soils in Northern British Columbia

AbstractTillage management practices may affect crop growth, in part by altering soil thermal properties. Effects of long‐term conventional (CT), no tillage (NT), and modified no tillage (NTR: NT with surface residue pushed away from a 7.5‐cm zone over the seed rows) systems on soil thermal conductivity (K) and water content (θ) were evaluated on Donnelly silt loam and sandy loam (Typic Cryoboralfs). Measured K (M1) was compared with calculated K using the McInnes equation (M2) and a modified McInnes equation (M3, which included additional soil properties). The K in both soils increased with an increase in soil θ; the differences among the tillage systems decreased as the soil dried. Soil K for the silt loam was 0.81 (θ = 0.13 m3 m−3), 0.83 (θ = 0.14 m3 m−3), and 0.84 W m−1 K−1 (θ = 0.15 m3 m−3) in CT, NTR, and NT, respectively, at 25 d after planting in 1992 (a dry year). It was 1.13 (θ = 0.42 m3 m−3), 1.53 (θ = 0.50 m3 m−3) and 1.55 W m−1 K−1 (θ = 0.57 m3 m−3) in CT, NTR, and NT, respectively, at 47 d after planting in 1993 (a wet year). Soil K for sandy loam was significantly lower than for silt loam. Soil K measured by M1 and calculated by both the M2 and M3 methods were highly correlated. However, the calculated K values were somewhat improved, although not significantly, with the M3. Mean K was lower by 0.133 W m−1 K−1 in M2 and by 0.045 W m−1 K−1 in M3 than in M1 under CT on silt loam. Increased soil water storage under long‐term NT produced a greater thermal contact area and, consequently, a significantly greater K under NT and NTR than CT.

Subirrigated Bell Pepper Production with Reduced Water Table Levels and Fertilizer Rates

The effect of water table level and fertilizer rates on bell pepper production grown with the fully enclosed subirrigation (FES) system was studied over three fall growing seasons (1992–94). The FES system uses buried microirrigation tubing in the field to convey water for maintaining a water table level and has shown to achieve application savings of 30% to 40% compared to the conventional subirrigation method that maintains a high water table using lateral field ditches. Controlled water table levels of 45, 60, and 75 cm below soil surface and fertilizer rates of 1194, 1716, and 2239 kg·ha–1 (18–0–21 expressed as N–P–K) were used as treatments replicated in time over 3 growing seasons. The 45-cm water table level and 2239 kg·ha–1 fertilizer rate are considered the conventional commercial practices. Results showed that comparable seasonal production levels were achieved among fertilizer rates and water table levels with no significant interactions between treatments. These data indicate that using a lower target water table level allows lower rates of fertilizer to be used because the susceptibility of the fertilizer to leaching caused by excessive rainfall is lessened due to increased soil water storage capacity.

"Beyond Love"

Service crops (commonly known as cover crops) are plants grown in agroecosystems for the ecosystem services they provide rather than a harvestable product. One such service they provide is that of increased crop water supply. By reducing evaporative water loss and increasing soil water storage, storage capacity, and the successive crop9s ability to access stored water, service crops may be used to increase agroecosystem resiliency to seasonal water deficits and so improve crop yields. In many instances, however, these benefits are not realized. This is more likely a consequence of suboptimal management, or management tailored to provide other services, rather than the ultimate capacity of service crops to contribute to agroecosystem resilience. After reviewing the literature, we propose that service crop polycultures—in contrast with monocultures—have the greatest potential to provide this service, and that, if properly managed, a grass/legume/taproot service crop mixture could maximize multifunctionality while also offsetting the challenges associated with the component species when grown in monoculture.

Water‐Yield Relationships for Irrigated and Dryland Wheat in the U.S. Southern Plains

AbstractA climate with high evaporative demand and limited precipitation restrict yields of winter wheat (Triticum aestivum L.) grown in the semiarid U.S. southern High Plains. Stress effects can be avoided or minimized by management practices that increase soil water storage at planting or by application of irrigation water. We analyzed a 178 crop‐year database of irrigated and dryland wheat data from Bushland, TX, to develop relationships that define the grain yield and water‐use efficiency (WUE) response to a wide range in seasonal evapotranspiration (ET) associated with water deficits and to evaluate yield response to stored soil water at planting. The ET‐grain yield relationship was determined as linear, with a regression slope of 1.22 kg grain per m3 ET above the ET threshold of 208 mm required to initiate grain yield. Maximum yields (>7.0 Mg ha−1) required 650 to 800 mm seasonal ET. Maximum yields observed in the combined database were 2.8 and 8.2 Mg ha−1 for dryland and irrigated wheat, respectively. The linear regression response of grain yield to soil water stored at planting, 1.57 kg m−3, was significantly higher than the yield response to seasonal ET. Largely similar WUE values occurred over a wide range of seasonal ET within irrigated and dryland data sets; however, WUE values for irrigated wheat averaged about double the values for dryland wheat. A curvilinear relationship determined between WUE and yield emphasizes the importance of obtaining high yields for efficient water use.

Ridge tillage for continuous grain sorghum production with limited irrigation

Improved soil and water conservation are basic goals for crop production systems in the semi-arid southern Great Plains (SGP) of the USA and similar regions, and managing crop residues on the soil surface plays a key role in attaining these goals. Residue production by dryland grain sorghum ( Sorghum bicolor (L.) Moench) is often too low in semi-arid regions to improve soil and water conservation, but much greater amounts are produced by irrigated sorghum. However, irrigation water may be limited, as in the SGP, and a limited-irrigation approach is sometimes used for sorghum, which responds well to timely irrigations. This study, conducted on Pullman clay loam (fine, mixed, thermic Torertic Paleustoll) from 1986 to 1992, determined effects of residue management treatments involving ridge tillage on continuous production of two grain sorghum hybrids with limited irrigation. Treatments were conventional (ConvT) tillage, which involved stalk shredding, disking, and rebuilding of the ridges soon after sorghun harvest, and two ridge tillage methods (residues shredded early (at harvest) — ConsTE; residues shredded late (at planting) — ConsTL). Soil water storage between crops was greatest with the ConsTL treatment and least with the ConvT treatment. Soil water use by sorghum was greater (66 mm) with ConsTL than with ConvT (51 mm). Mean initial plant populations and panicles harvested were greater with ConvT than with other treatments, but grain yields were less with ConvT (4.21 Mg ha −1) than with ConsTE (4.42 Mg ha −1) and ConsTL (4.52 Mg ha −1). Mean stover yields and seed weight (mg per seed) were not affected by tillage treatments. Although differences were relatively small, mean grain and stover yields were greater for the ‘Pioneer’ cultivar (4.53 and 5.68 Mg ha −1) than for the ‘Funk’ cultivar (4.24 and 5.25 Mg ha −1). Mean water use efficiency differences among treatments and between hybrids were small. Ridge tillage was better than conventional tillage for continuous grain sorghum production with limited irrigation in the semi-arid SGP. Ridge tillage that retained residues on the surfaces until planting increased soil water storage due to reduced evaporation and increased snow trapping, which resulted in the greater yields than where residues were incorporated with soil soon after crop harvest.

Field determined hydraulic properties of a sandy loam soil irrigated with various salinity and SAR waters

Changes in the infiltration, drainage, soil-water characteristics and unsaturated hydraulic conductivity were evaluated in field plots of a sandy loam soil irrigated with waters of different salinities (EC w 6 and 12 dS·m −1) and sodium adsorption ratios [SAR w 5, 20 and 40 ( mmol.·1 −1) 1 2 ] for a period of 8 years. Unsaturated hydraulic conductivity, K( θ), for the various treatments was determined by measuring hydraulic gradients and soil-water contents from simultaneously evaporating and draining profiles, as well as from draining profiles with no evaporation. Relative infiltration rate (RIR) was calculated considering steady infiltration in the original soil (22.5 mm·h −1) as the reference relationship. When measured using canal water (EC w 0.7 dS·m −1), RIRs were reduced to 0.64–0.90, 0.10 and 0.05–0.07 in soils irrigated with SAR w 5, 20 and 40, respectively. Long-term use of higher salinity waters but with similar SARs caused greater deterioration. When waters of various salinities and SARs were used for measuring infiltration, the RIRs at SAR w 5, 20 and 40 ( mmol·1 −1) 1 2 were increased to 0.96, 0.79 and 0.42 in soils irrigated with EC w 6 dS·m −1. Likewise, RIRs were increased to 0.67, 0.35 and 0.27 for an EC w of 12 dS·m −1. Stability of the surface soil and thus permeability should have improved during infiltration of saline waters with electrolytic concentrations more than the flocculation values, but the small improvement in infiltration rates indicate that deeper soil controls the steady infiltration rate. The dispersed state of the deeper layers in soils irrigated with high SAR waters was further evident from increased soil-water retention at lower matric potentials in the tensiometric range, as well as being reflected in decreased values of drainage coefficients and increased soil-water storage. Unsaturated hydraulic conductivity K( θ), could be adequately described ( r = 0.87–0.97) by the equation K = α exp·( βθ). Values of K( θ), when referenced to the original soil, ranged between 0.56 and 1.12 at θ = 0.3 but were reduced 2- and 4-fold at θ = 0.1 m 3·m −3 for soils irrigated with waters of SAR w = 20 and 40 ( mmol·1 −1) 1 2 , respectively. Results indicate that the laboratory determinations may not assess adequately the changes in hydraulic properties upon irrigation with high-SAR saline waters in soils undergoing cycles of salinization and desalinisation under a continental monsoon climate.

Residue Management for Winter Wheat and Grain Sorghum Production with Limited Irrigation

AbstractWinter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are extensively grown in the southern Great Plains on dryland and with irrigation, but yields often are low on dryland and irrigation water is limited. Because both crops respond well to timely irrigation, they sometimes are grown with limited irrigation. Thus, it was hypothesized that using limited irrigation for these crops would produce sufficient residues to increase soil water storage if conservation tillage practices were used. This study on Pullman soil (fine, mixed, thermic Torrertic Paleustoll) at Bushland, TX, determined the effects of residue management on soil water storage and use, yields, and yield components for wheat and sorghum grown in rotation with limited irrigation. Treatments were no‐tillage with standing (T1) or shredded (T2) residues, and no‐tillage after wheat and tillage after sorghum (T3). Tillage did not affect water storage after wheat, but storage ranged from 68 mm with T3 to 101 mm with T1 after sorghum. Water use by wheat ranged from 93 mm with T3 to 131 mm with T1, but tillage did not affect water use by sorghum. Tillage did not affect wheat yields because differences in soil water storage and use were small and irrigations minimized the water content differences. Tillage did not affect sorghum yields because using no‐tillage during fallow after wheat resulted in similar water storage in all cases. This study showed that practices that retain surface residues are effective for producing wheat and grain sorghum in rotation under limited‐irrigation conditions in the southern Great Plains.

Evapotranspiration and Yield of Beans as Affected by Mulch and Irrigation

AbstractMulch (crop residue) has been reported to increase soil water storage and crop yield, and to reduce soil water stress under some conditions. However, few studies have had irrigation, and thus evapotranspiration (ET), as a variable where soil water was controlled. Therefore, a study was conducted to evaluate the effect of mulch on ET, bean yield (Phaseolus vulgaris L.), and water use efficiency (WUE), under a wide range of irrigation levels. Treatments were two cultivars (Viva‐Pink and Red‐63), two mulch rates (bare, and 7.0 Mg ha−1 of wheat straw), and six irrigation levels (from 0.0 to 288 mm) for 2 yr. Different irrigation levels were achieved by a line source sprinkler. Evapotranspiration was estimated from measurements of irrigation, precipitation, soil water depletion, and estimated drainage. Transpiration (Tr) was estimated from a function of relative yield and relative ET. Dry matter and seed yields were significantly greater for mulched than for bare plots. Mulched plots had a higher WUE (yield/ET) than did bare plots for a given irrigation level but increased as irrigation level increased. Seasonal differences in ET between bare and mulched plots were small. The yield‐ET relation for mulch was linear but was distinctly different from bare soil, indicating a different partitioning of ET into soil water evaporation (Es) and Tr. For the conditions of this experiment, mulch reduced Es by about 45 mm, at the same ET, and Tr was increased by 45 mm. However, for tbe same irrigation level, ET was lower for mulched than for bare plots, indicating that not all of the water saved went to Tr.

Impact of tillage and residue management on dryland spring wheat development

No-till or reduced tillage practices are frequently recommended to reduce wind and water erosion and to increase soil water storage. Grazing stubble after harvest or producing crops with low residue may negate the benefits of the tillage practices. In this study, we determined the effects of tillage and residue management systems on the growth and development of the subsequent spring wheat ( Triticum aestivum L.) crop. The study was conducted for 2 consecutive years in eastern Washington, USA. The soil was a (Chard) silt loam. Tillage treatments were conventional (spring sweep and summer cultivation) and no-till (chemical fallow). Residue management treatments were: (1) all crop residues removed at the beginning of the 21-month fallow period; (2) all surface residues removed after the first winter rainy season; (3) no residues removed. For the 1988 crop year, 3.0 Mg ha −1 of winter wheat residue and for the 1989 crop year 0.7 Mg ha −1 of barley ( Hordeum vulgare L.) residue was present at the beginning of the fallow period. Growing season precipitation was 153 mm in 1988 and 91 mm in 1989. Water use efficiency and grain yields were generally higher in 1989 than in 1988. No differential germination or emergence stresses owing to treatments were found in either year. In 1988, stored water at the time of planting was lower where surface residues had been removed than where they had not been removed and, by anthesis, plants in the residue removal treatments began to show signs of water stress. Relative water content of flag leaves of these plants was lower than when residue was not removed and the plants also lost more tillers. At maturity, the reduced number of heads m −2 and seeds per head led to a reduction in final grain yield of about 0.5 Mg ha −1. In 1989, a better crop year, no significant treatment differences were observed at any stage of development. These results illustrate the importance of proper residue management, especially in moisture limiting environments.

Cropping practices in the Victorian Mallee. 2. Effect of long fallows on the water economy and the yield of wheat

Two experiments were conducted at the Mallee Research Station, Walpeup, between 1985 and 1989 to determine whether increases in wheat yield that occur after long fallows result from improvements in the supply and use of additional soil water conserved during the fallow. Although long fallows increased the amount of water stored in the soil at sowing (average 22 mm) and the yield of wheat (0.26 to 1.37 t/ha) in the first experiment, the results suggest no causal relationship between these increases. Improvements in wheat yield were attributed to increases in soil nitrogen availability and to control of cereal root diseases rather than to any increase in soil water conservation. This was confirmed in the second experiment, which was managed to ensure that nitrogen supply and cereal root diseases were not limiting crop production. Increases in soil water content at sowing resulting from long fallows did not result in higher wheat yields. This study suggests that long fallows cannot be justified on the basis of this increased soil water storage, as much of the additional soil water accumulated during the fallow period is stored in the lower part of the rootzone. Movement of this water below the rootzone during the growing season appears to be the main reason for the additional water stored at sowing, with long fallows failing to increase wheat growth and yield.

Ridge Height and Furrow Blocking Effects on Water Use and Grain Yield

Because water supplies are limited for crops in the Great Plains, use of water-conserving practices is important. This study determined the influence of ridge height and furrow blocking on water conservation and use, and yields of irrigated winter wheat (Triticum aestivum L.) and dryland grain sorghum [Sorghum bicolor (L.) Moench] grown in rotation. The rotation results in two crops in 3 yr with a 330-d fallow between each crop. The study was conducted from 1981 to 1990 at Bushland, TX, on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Ridge heights were 12 to 15 or 5 to 8 cm and furrows were blocked or open. The ridge-height and furrow-blocking treatments were imposed every 3 yr before planting wheat. No-tillage was used during fallow after wheat and reduced tillage was used to reform the ridges during fallow after sorghum. Water infiltration was little affected by treatments. Differences in soil water content at planting and harvest were significant in some cases, but trends were inconsistent. Total water use was not affected by ridge height, but was greater with open than with blocked furrows for wheat. Although significant in some years, mean wheat and sorghum yield differences were small. On gentle (<0.5%) slopes, furrow blocking in combination with notillage and reduced tillage did not increase soil water storage or crop yields over those obtained with no-tillage alone. There was no indication that long-term no-tillage and reduced-tillage practices adversely affect wheat and grain sorghum production.

Breeding for hard red winter wheat cultivars adapted to conventional-till and no-till systems in northern latitudes

Conservation tillage in the Great Plains of North America has increased in recent years, in part, to control soil erosion, increase soil water storage and reduce production costs. No-till production is recommended for winter wheat (Triticum aestivum L.) in northern latitudes for the purpose of trapping snow and protecting the crop from freezing temperatures. A 5 year field study was conducted at four North Dakota locations from 1984–85 through 1988–89 to determine if significant cultivar x tillage interactions existed for grain yield of winter wheat. Fourteen hard red winter wheat cultivars were planted in both conventional-till and no-till systems. Significant cultivar x tillage interactions were obtained for grain yield from both a weighted analysis across all environments and from individual analyses of 12 of the 16 environments in which wheat survived under both tillage systems (P 1.0. Although the cultivar x tillage interaction may be a result of differential winter survival rather than tillage per se, this study suggests that selection for winter wheats with superior yield performance can be conducted under either no-till or conventional-till systems.

Snow hydrology of a headwater Arctic basin: 1. Physical measurements and process studies

The hydrologic cycle of an arctic watershed is dominated by such physical elements as snow, ice, permafrost, seasonally frozen soils, wide fluctuations in surface energy balance, and phase change of snow and ice to water. Hydrologic data collected over a 5‐year period (1985–1989) from an arctic watershed in northern Alaska are presented. Processes related to snow accumulation, redistribution, ablation, evaporation and subsequent snowmelt‐generated runoff are discussed. The total water content of the snowpack at the end of winter has comprised between 28 and 40% of the annual precipitation. Redistribution of snow on the ground by the wind is a major factor in increasing the snowmelt runoff. Much of the redistributed snow accumulates in the valley bottom along the stream and also along depressions on the hillslopes. These depressions are small surface drainage channels that are referred to as water tracks. Partitioning of the snowmelt into runoff, evaporation and increased soil water storage in the active layer was carried out on the plot and watershed scale. Over a 5‐year period, the volume of snowmelt runoff varied from 50 to 66% of the average watershed snowpack, while evaporation varied from 20 to 34% and soil moisture storage increased between 10 and 19%. Much greater variation in these hydrologic components occurred at the plot scale.

Basin tillage

Basin tillage is a soil and water conservation practice that increases surface depression storage of precipitation, thereby potentially reducing storm runoff and increasing soil water storage and availability to crops. In this short review, we discuss the historical development of basin tillage, describe different types of equipment used for constructing the basins, and discuss the application of the practice to production of dryland and irrigated crops.

Bare Fallowing on Sandy Fields of Niger, West Africa

AbstractAn experiment was conducted in three rainfall zones of Niger, West Africa, to evaluate the potential of mulched and nonmulched bare fallow to conserve water in deep, sandy soils. Water content of adjacent bare and cropped experimental plots was monitored with a neutron probe at three sites during the 1985 growing season and the subsequent dry season. Experimental sites, with soil type and 1985 rainfall, were near the villages of Chikal (Ustic Torripsamment; 233 mm) N'Dounga (Psammentic Paleustalf; 344 mm), and Kala Paté (Alfic Ustipsamment; 428 mm). Cropped plots were managed using traditional low‐input practices. Bare plots were weeded using a traditional, shallow cultivating hoe. At the end of the growing season, portions of the bare and cropped plots were mulched with millet stalks at a rate of 25 Mg ha−1. At the end of the dry season, no significant increases in profile water storage were detected in mulched treatments. Increased soil water storage in the upper 1.65 m of bare fallowed plots toward the end of the dry season was 16.5 ± 10.5 mm at Chikal, and 40.6 ± 17.9 mm at N'Dounga. No increase in storage was observed in bare fallowed plots at Kala Paté. Mean increases in storage efficiency at Chikal and N'Dounga were 7.1% and 11.8%, respectively. Position of the zero‐flux boundary during the dry season and profile water distribution toward the end of the dry season indicate that drainage was substantial at all sites. However, large losses due to evaporation are also possible, due to high evaporative demand during the dry season. Data obtained in this study suggest that bare fallowing, with and without dry‐season mulching, is an inefficient means of water conservation for these soil systems. A possible application of bare fallow is in sandy soils underlaid by laterite in high‐risk, low‐rainfall zones of the Sahel if accompanied by adequate erosion prevention.

A Conservation Tillage System for Profitable Cotton Production in the Central Texas High Plains

AbstractIrrigation water supplies are dwindling in the southern High Plains and effective methods of conserving precipitation during fallow periods are needed. This study was conducted to compare soil water storage, yield of cotton, and profitability of conventional and notillage in a 2‐yr, double crop, irrigated barley (Hordeum vulgare L.)‐ dryland cotton (Gossypium hirsutum L.) cropping sequence with a 48 wk fallow from barley harvest and cotton planting. The soil was a Sherm (fine, mixed, mesic Torrertic Paleustolls) clay loam with 2.2% organic matter, a soil pH of 6.9, and 28, 31, and 41% sand, silt, and clay, respectively. Kochia [Kochia scoparia (L.) Schrad.], Russian thistle [Salsola kali (L.) var. tenuifolia Tausch], pigweed (Amaranthus blitoides S. Wats.), and witchgrass (Panicum capillare L.) were controlled during fallow with disk and field cultivator in conventional tillage. Herbicides used for no‐tillage were dicamba [3,6‐dichloro‐2‐methoxybenzoic acid], atrazine [6‐chloro‐N‐ethyl‐N′‐(l‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], fluometuron [N,N‐dimethyl‐N′‐[3‐(trifluoro‐methyl)phenyl] urea], and glyphosate [N‐(phosphonomethyl)glycine]. A 45 mm increase in soil water storage with no‐tillage increased dryland cotton yields 110 kg ha−1. Although herbicide costs were $155.00 ha−1 greater with no‐tillage, long‐term annual profit with no‐tillage increased $82.00 ha−1 over conventional tillage because of increased yield and lower machinery depreciation Costs.